Here's a beauty with a Mega billet side charging upper and Young Mfg side charging match carrier. The PRI carbon fiber forearms are some of our favorites. The Mega billet upper receiver is outstanding:

Last but not least for this post is a rifle based on receivers from Spike's Tactical. A Troy TRX Extreme 13" forearm completes the build with the 18" Bison SPR 6.8 SPC barrel: